Last September, CFMOTO surprised us by revealing undercover prototypes of two new sports bikes, the 675RR and the 500SR, the former with a 675cc three-cylinder engine and the latter with a 600cc four-cylinder engine. Now, the company has filed patent applications relating to the 500SR’s engine to give us our first look inside.
Although CFMOTO showed the 675SR’s 675cc three-cylinder engine at EICMA in November last year, confirming its layout and offering some vague performance claims, including a power figure of around 100 hp at 12,300 rpm. The 500SR remains a mystery. A prototype took a few public demonstration laps on a track in China last year, along with the 675SR – with both bikes heavily disguised with camouflage to keep technical details and styling hidden – but apart from revealing that the bike makes as much noise as you’d expect from a 500 cc bike, little has been revealed.
The new patent applications refer to some common engine elements, focusing on a cooling system that is designed to bring the engine up to operating temperature as quickly as possible, probably to help meet increasingly stringent emissions limits that include cold start tests. However, the documents include diagrams of the engine that give us a clear view of its layout and internal components.
The images clearly show that the engine was designed by CFMOTO – after all, there aren’t many modern 500 cc in-line engines on the market, even if the company wanted to copy a rival – and that it is a fairly conventional, high-performance four-cylinder engine. Details include chain-driven double overhead camshafts, with the chain at one end of the crank rather than in the middle. We can also see that there are four valves per cylinder and coil-on-plug electronic ignition.
There’s a conventional six-speed transmission – last year’s prototype may have been disguised, but the clutch and gear lever were clearly in view, so there’s no semi-automatic trickery here – and a wet sump that’s offset to allow space for the exhaust system to pass underneath.
As far as performance is concerned, we can logically expect the 500SR to sit below the 675SR in CFMOTO’s power pyramid, falling between the 100-plus hp three-cylinder and the 449 cc, 50 hp two-cylinder 450SR. As a direct rival to the smaller fours, including Kawasaki’s Ninja ZX-4RR and Kove’s 450RR, CFMOTO will try to get around 80 hp from the 500SR.
When it is launched later this year, the 500SR will be another step in the unexpected revival of small-capacity fours, a class that seemed doomed by tight emissions rules and the trend towards cheaper-to-manufacture twin-cylinder engines.
Source:https://www.cycleworld.com